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Nick F

Senior forecaster
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Everything posted by Nick F

  1. The divergence between the models post day 6, 00z EC vs GFS, UKMO, GEM, ICON - appears to be how they handle the deepening winter storm off the east coast of US and Canada over the weekend and into next week. EC drives the deep low north up through the Labrador Sea towards Baffin Bay, driving WAA north over the Atlantic towards Greenland and Iceland building a strong mid-Atlantic ridge. Whilst the other models have the low moving NE towards tip of Greenland keeping the upper flow across the N Atlantic a lot flatter. EC T168 GFS T168 GEM T168 US forecasters yesterday placing a lot of uncertainty over the storm developing near the east coast, due to how a shortwave trough in the upper flow coming in off the Pacific deepens as it moves across the US and interacts with frontal boundary over the eastern US. And whether this shortwave trough lifts north or northeast over eastern Canada and upper flow amplifies over the NW Atlantic may impact our fortunes early next week.
  2. 00z GFS op at the cold end of the ensembles spread, but not without support. usually GFS has a good track record with modelling northerlies at range, though the 00z op probably at the extreme end wrt depth of cold and duration, given EC is much less cold and shorter in duration with the northerly, while GEM and ICON don't look to entertain the idea of a northerly at all. So caution required if getting too excited looking at those T850 and precipitation charts from GFS.
  3. Lala land I know, but with a trough dug out across Europe by then and bulging ridge over the Atlantic, chance for a northerly reload?
  4. Probably going to have to take a second warming later in Feb to do more meaningful damage than what is now currently being shown by the models. The SPV won't give in easily this winter.
  5. Well fingers crossed the amplification in the upper flow early-mid next week comes off to allow a proper cold northerly that can bring a flake of snow even to the south. Because it looks, for now, that it may take second warming later in Feb to perhaps finally knock out the wretched strong SPV that has ruined the winter for cold and snow lovers thus far. 18z GFS certainly putting on a good show.
  6. Wasn't aimed at you, apologies if it appears that way, just generally an observation of some knee-jerk reactions to pro met tweets over the years and last few days with the SSW, as if their word is the likely outcome. I agree with you, westerlies is a possible outcome still, particularly as the models appear to be backing away from a SSW ... for now and we're left with a restrengthening SPV. Though the warming is still on and a displacement of the SPV may still work in our favour.
  7. It does concern me that some hang on every word of meteorologists, like they know for sure how the troposphere will be affected by potential changes in the stratosphere beyond 7 days, no-one can know with confidence what will happen, given each model is spewing out different outcomes from elongation, splits or displacements. And his tweet the other day said to 'take with a huge pinch of salt' anyway.
  8. The way our luck has gone so far this wretched winter, you'd have to go for Monday morning blues after the high spirits before closing time the night before from the model output. But, you never know, our luck might change. Boy do we deserve it! Even if it's a two day northerly toppler.
  9. Funny how the 18z generally produces the BOOM charts. Again days 9-10, so can't be relied on. But the 12z EPS mean and recent operational runs of various models hint at amplification of an Atlantic ridge in this timeframe. Just so far we haven't got as amplified as the 18z GFS.
  10. Still signs of major stretching and possible split down the line in the stratosphere polar vortex on 12z EC day 10, how this eventually penetrates down to the troposphere remains to be seen, some mirroring there in the trop, but can't really say it's coupled all round the northern hemisphere Day 10 EC 10mb (stratosphere) Day 10 EC 500mb (troposphere) Day 10 EPS trop 500mb mean
  11. I don't see any split in the troposperic vortex on the 12z EC, just lobes of the vortex days 9-10, one over NW Atlantic/NE Canada the other over NE Europe/ NW Russia, with the UK in between. Still deep low heights over the arctic where the TPV is centred. As a result, any cold N/NWly shot on the operational run could be transitory, before the ridge between the lobes or troughs of the TPV collapses and the upper flow flattens out again to westerlies or southwesterlies. However, 12z EPS extended: ridging signal over NW Europe theme continues days 10-15 seems rinse and repeat of a few weeks of unsettled then week of high pressure this winter. But high pressure never gaining latitude to bring proper cold.
  12. Note he says 'huge pinch of salt'! Just one EC run! Wouldn't hang on every word that's posted on social media, even pro mets. As well as uncertainty in the strat, MJO uncertainty too. After a brief visit in 6 both EC and GEFS go back into COD, EC stays in there but GEFS comes out in P2 then over to 3. Could lead to some different outcomes from models.
  13. I wouldn't worry too much for now, there's no knowing how the SPV will 'react' to the forecast warming, it may be elongated as per charts in the tweet but the GFS eventually displaces an intact SPV towards Russia/NE Europe on 06z. And we won't know how the trop will be affected by this possible shakeup in the stratosphere
  14. Gaining momentum by the day on GEFS. May not see effects until end of Feb to early March if a SSW were to transpire.
  15. Yes, this slowing of zonal winds certainly seems to have more mileage this time round, plus some of the EPS members in the 10-15 day range have been showing a reversal lately. Seasonal weakening of SPV would be expected as we head through Feb too, which will help. Then if a major SSW occurs we need to hope the response is quick and favours HLB that would position favourably to bring sustained cold to the UK. Lots of hurdles to get over, that’s after we do get a reversal in the bag!
  16. Definite trend downwards starting to show in GEFS in early Feb, some members going negative, but we've been down this garden path before in December at that range, need to get into the reliable to start getting interested
  17. Yep, the strong coupled strat-trop PV is fending off high/++AAM and MT poleward momentum into the mid/high latitudes and any poleward amplification from the MJO wave the same - kept towards the tropics. With regards to the QBO, only easterly above 30 hPa over the tropics, whole lot of zonal westerlies north of that. Our winters tend to benefit most when we come out of the solar minimum, on average, so maybe the next few winters will fare better. I guess we have to hope that the strat-trop coupled PV becomes weakened and/or displaced towards NE Europe as we head through Feb, signs of that in GFS, to be the catalyst to a pattern change, but probably will be a slow process.
  18. That's not a -NAO though, pressure still quite a bit lower over Iceland than over the Azores, if there's high pressure over Iceland and low pressure over Azores to Lisbon then yes. Not expecting 00z GFS to repeat 18z moment of wintry euphoria, enjoy the virtusl cold and snowfest while you can!
  19. Was wondering when a GFS operational would bring back from the dead a northerly. 12z extended EPS mean indicates the postive height anomaly / HLB over Canada slowly migrating towards Greenland by day 15, while a negative H500 anomaly persists over Scandinavia. This perhaps highlights potential for northerlies and this movement of positive heights out of Canada appears to be the catalyst for the 18z GFS northerly in FI. However, troughing modelled over the mid-Atlantic towards Azores needs to do one, as per 18z, in order to do this.
  20. Winter's over? 18z GFS hardly inspiring, bar brief windows on Sunday, then next Tuesday/Weds for the north, which could get cold enough certainly for the hills to get a covering of snow, maybe pushing it though to lower levels. Good news for the Scottish ski industry. The trend of the models of digging a trough in the Atlantic by day 10 and raising heights over SW Europe is not a good signal either.
  21. Would err on the side of caution with the GFS, it often has a cold bias in the medium range with depth of cold in polar maritme flows when they reach the UK, most of the time the flow ends up not as cold as progged, partly because it pushes the jet too far south and perhaps doesn't pick up secondary waves until nearer the time, which ultimately hold back the colder Pm flow or dilute it with less cold air. That's not to say it won't get as cold as the 12z op is showing, but it's worth not getting too excited at this range for snow, away from favoured northern hills.
  22. Central pressure of intense anticyclone centred over SW England Sunday night could reach 1050 hPa, last time this happened was 16 Jan 1957. View the full blog here
  23. Good question, and difficult to answer definitively, depends exactly where the blocking sets up I suppose. If it's over Greenland/Iceland, a southerly tracking jet underneath may not bode well, though depends whether the corresponding -NAO is west based or east based. West based wouldn't be so bad, as we'd be on the warm side of Atlantic troughing, east based not so great. Block over Scandi not too bad in summer with an easterly flow being dry and warm.
  24. It did look hopeful for a time that the MJO would go through 7 and get to phase 8 at decent amplitude, phases that at good enough amplitude can lead to northern/high lat blocking and -NAO further down the line, given the lag of 10-12 days. However, it looks like we are getting the response of the wave through phase 6 leading to blocking high pressure over the UK/Europe (MLB) but the response from the move into phase 7 is looking rather muted in recent model output. One explanation, that I read by Isotherm a US weather expert on another forum, is that the wave of strongest convection over the Pacific is tending to be along the equator and the southern hemisphere tropics of the Pacific - so this is having less impact on the upper flow of the northern hemisphere than was hoped. Given the background state of the strong TPV since mid-December, what little amplification is being made from the convection in the colder phases is having a very muted effect. Couple this with convection firing over the Maritime continent (warm phases) and the ongoing effects if the Indian Ocean Dipole - it appears the MJO does not want hang around or get into colder phases at decent amplitude this winter. But prefers to spend longer in warmer phases. With regards to hoping the eQBO will help us out, again, not as clear cut, yes the QBO is easterly high up in the stratosphere, but it still has yet to descend lower down into the lower stratosphere and certainly far from denting the strong zonal winds at high latitudes - though signs it will do this through February, so may help weaken the PV with time and perhaps allow northern blocking as we end winter. The models still forecasting a decrease in 10 hPa zonal winds in the stratosphere, but its dropping from a very high spike and so forecast, so far, only get to the climatology average - given zonal winds tend to drop anyway on average as we go towards March. So where does that leave us? Nothing showing from the main drivers to change the pattern for a few weeks, though worth keeping an eye on the blocking centred over central Canada perhaps extending its influence towards NW Atlantic and even western Greenland - this *could* be enough to orientate an increasingly cyclonic NW to SE flow across NW Europe as we end January..
  25. With little amplification showing in the northern arm of the jet north of the UK and the mid-latitude high building from this weekend, thanks to the omnipresent strong TPV over Greenland/arctic, there is no impetus for the MLB to go anywhere other than hang around NW Europe or perhaps migrate west for a time. Ideally we want the high to move NW so as to get a northerly, but that ain’t gonna happen with the strong flat jet north of the UK. It appears the models are putting more energy into the STJ over N America and eventually into the N Atlantic, perhaps due to increasing Nino-esque forcing over the Pacific, with heights lowering towards the Azores in the means, but with low heights persisting over Greenland, that pushes the MLB back into Europe with the dreaded mild SWly for the UK. Only straw to clutch is that the models are misreading the signal from the MJO, a conflicting signal because as well as a wave of convection firing over Pacific and moving into western hemisphere (colder phases 7-8-1) there is also some convection firing over the Maritime continent (warmer phases) – which may be why the models are trying to put the MJO into COD rather than moving through 8, given the strong convection signal shown on the VP200 forecasts. However, it may be an uphill battle getting amplification over the Atlantic given the strong TPV trying to keep the jet flat. Fingers crossed that the TPV gets displaced and weakens as we head through feb to allow the jet to weaken and allow more amplification. The wait continues to see if we can salvage something out of this awful winter so far for cold and snow lovers.
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